The consensus on placement of the family is with the Dasyuromorphia order, with agreement on the divergence this family and the Dasyuridae, represented by the extant quolls and Tasmanian devil Sarcophilus harrisii, remaining under consideration.

The thylacinid family was represented by two species in a synonymy published in 1982, the recently extinct Tasmanian tiger and the species Thylacinus potens, known by fossil material. Discoveries of new material, especially in well researched fossil depositions at the Riversleigh World Heritage Area, revealed a diverse array of genera and families existing during Miocene epoch. The dentition of specimens and some largely complete crania showed the development of specialist predators capable of hunting and consuming a range of vertebrate species, and like other mammalian predators, such as the canid family, could include herbivores larger than themselves. An assessment of the size range of the species has provided evidence of animals occupying a greater number of trophic levels and challenged the conception of the dominance of reptilians as large hyper-carnivorous predators on the Australia continent.[1]

The consensus of authors prior to 1982 was that the thylacinid family were related to the borhyaenoids, a group of South American predators, also extinct, that exhibited many similar characteristics of dentition. A review published in 1982 compared the skeletal structure of these groups, concluding the tarsal bones show greater affinity with the dasyurmorphs, strongly supporting the later theory that any dental similarities emerged independently.[2]

Another family, the Thylacoleonidae, were also large carnivorous marsupials, but allied to the order Vombatiformes and assumed to have also evolutionarily converged as predators of large herbivores.

^Wroe, Stephen (1995). "Muribacinus gadiyuli (Thylacinidae: Marsupialia), a very plesiomorphic thylacinid from the Miocene of Riversleigh, northwestern Queensland, and the problem of paraphyly for the Dasyuridae (Marsupialia)". Journal of Paleontology. 70 (6): 1032–1044. doi:10.1017/S0022336000038737.